Patent GB-851996-A (GB)
Title: A change speed transmission
IPC: F16H61/02
Filed: 1957-01-15
Abstract: 851,996. Change-speed control. FULLER MANUFACTURING. CO. Jan. 15, 1957 [March 5, 1956], No. 1513/57. Class 80 (2). The input and output shafts 2, 3 of a countershafttype five speeds and one reverse gear, for a heavy vehicle, drive a pilot synchronizing detector unit, having stepped or stepless ratios corresponding to those of the main gear, and providing a signal when the gear ratio next to be engaged is in a non- synchronous condition, but is approaching, at a predetermined period ahead, exact synchronization, such signal causing engagement of said ratio at substantially exact synchronization. An automatic countershaft brake 35 is used to synchronize upshift, whilst downshift is synchronized by the operator accelerating the engine. During shift the main clutch 7 is disengaged by a power cylinder 44 and remains disengaged throughout the whole of an upshift, whilst during downshift the clutch is re-engaged on reaching neutral and remains engaged during the synchronous establishment of the new ratio. Shift may be controlled manually or by unspecified automatic means. The main gear 1 comprises aligned input and output shafts 2, 3, a countershaft 4 and three shift rods 21, 28, 34, actuated by supplying compressed air from a source 194 to cylinders 52 &c. through a manually operated piston selector valve 64. Neutralizing is effected collectively by two plates 50, 55 which pick up collars 46 on the shift rods when closed together against a fixed stop 45 by supplying pressure to a neutral cylinder 57. The synchronizing pilot gear 100 comprises input and output shafts 143, 106 continuously driven respectively by the input and output shafts of the main gear 1. The shaft 106 carries fast wheels meshing wheels 116 ... 120, Fig. 2, freely mounted on a parallel shaft 102, each of the five wheel-pairs having a ratio equal to a corresponding one of the five forward ratios of the main gear. The shaft 102 is driven continuously by the shaft 143 through either of two wheel-pairs 142, 126; 141, 136, having ratios slightly above and below unity respectively, the former being used for upshift, the latter for downshift, so that in each case the pilot gear attains synchronism slightly in advance of the main gear. Selection between these two wheel-pairs is effected by moving the wheels 126, 136 together axially in either direction to engage frictionally a double cone 128 fast on the shaft 102. Fluid pressure applied at 229 to a piston 132 thrusts the wheels left to clutch the wheel 136, for downshift synchronizing, whilst a spring 132 thrusts them right to clutch the wheel 126 for upshift. Synchronism is actually detected by axially slidable splined sleeves 151 a selected one of which, simultaneously with the application of shift pressure to the corresponding shift rod in the main gear, has axial pressure applied to it in the appropriate direction to approach that one of the freely mounted wheels 116 ... 120 corresponding to the ratio to be selected in the main gear. The sliding sleeve 151 does not clutch the corresponding wheel, but merely applies axial pressure through balk-teeth to a coned balk-ring, e.g. 158, which is in continuous frictional engagement with the adjacent wheel, e.g. 117. When synchronism between the wheel 117 and shaft 102 is attained, the balk-ring 158 releases the sleeve 151 for rightward movement to actuate a trip valve 184 as follows. The splined sleeves 151 are actuated by shift-rods 168 ... 170, moved collectively to neutral by a spring 182 closing together two plates 174, 176, engaging collars 173 on the shift rods. Shift movement from neutral of any rod 168 ... 170, by fluid pressure applied to a selected one of five cylinders 172a, separates the plates 174, 176 and actuates the trip valve 184. Operation.-Neutral. The heavy lines in Fig. 1 show the circuit which is pressurized when the manual selector valve 64 is set at 76 in neutral. Starting. First speed is obtained by moving the manual selector valve 64 from position 76 through reverse 76a to first 76b. The manual selector valve 64 is frictionally connected at 92 to a direction-sensing " director " valve 63 which for all upshift movements it moves to the right against a stop 91 whilst for downshift it moves the valve to the left against a stop 89. The rightward movement to first speed is upshift and the director valve 63 is thus moved to the right. Pressure from the source 194 passes through a line 214, a neutral interlock valve 193, line 217, selector valve 64 and line 232 to the first speed shift cylinder 52b, but is without effect since it is overridden by the equal pressure supplied to the larger neutralizing cylinder 57, through a neutral-relay valve 191. The same neutralizing pressure 203, 204 passes through a line 223, the director valve 63 (rightward position) and a line 227 to apply the countershaft brake 35. The director valve 63 also exhausts a line 224 permitting a clutch relay valve 192 to spring left, supplying neutralizing pressure 203, 204 to release the main clutch 7 at 44. Also exhausted by the director valve 63 is the shift line 229 of the pilot gear drive selector, making the upshift gear pair 141, 136 effective, but although first gear shift pressure 232 is applied also to the first gear cylinder 172b of the pilot gear, this is without effect since the output shaft 106 is stationary and no balk-release can occur. To start the vehicle the operator depresses the usual main clutch pedal, and then pushes in a manual trip valve 211 to supply pressure from a neutral valve 58, operated by the neutralizing cylinder 57, and a trip line 208 to a line 209 to shift left the neutralizing relay . valve 191 (opposing pressure 221 on which has been exhausted through the manual selector valve 64 at 70). This exhausts the neutralizing and clutch-release cylinders 57, 44, the former permitting shift pressure in the cylinder 52b to assert itself and rapidly establish first gear, such movement also operating the neutral valve 58 to exhaust the trip line 208 and connected lines 222, 227, releasing the countershaft brake 35. Shift to first ratio is now completed and on release of the clutch pedal the vehicle starts. Upshift.-All upshift sequences are identical, the director valve 63 remaining in its right-hand position for exhausting the line 229 to select the upshift gear-pair 141, 136 for driving the pilot gear. 1-2 upshift is as follows. In moving from first speed setting 76b to second 76c, the manual selector valve 64 passes through an intermediate position where the following condition temporarily applies. A transverse pressure passage 73 in the selector valve 64 which, in gear settings 76a ... 76f, supplies pressure to the respective shift cylinders 52, in intermediate and neutral positions (shown) supplies pressure to a line 218 (exhausted at 70 in gear positions) and exhausts the shift cylinder pressure lines. Thus in the intermediate position between first and second speeds, the connected first speed main and pilot lines 232 are exhausted. Pressure 218, 221 shifts rightwards the neutral relay valve 191 to supply pressure direct to the neutralizing cylinder 57, and through the clutch relay valve 192 (now in its left position), to the clutch release cylinder 44, so that the gear is neutralized. Pressure 218 also shifts leftwards the neutral interlock valve 193 (opposing pressure 219 exhausted at the director valve 63), to exhaust the line 217, temporarily cutting off pressure from the selector valve 64 to ensure neutralizing of the gear at 57 before application of shift pressure. These actions occur instantaneously during passage of the selector valve 64 through the intermediate position, and when the valve 64 reaches second speed setting 76c, the line 218 exhausts at 70. Completion of neutralizing actuates the neutral valve 58, directing line pressure 196 to the trip line 208 (where it is ineffective); to line 222, director valve 63 and line 227 applying the countershaft brake 35; and to line 219 shifting the neutral interlock valve 193 right. This last action restores pressure to the selector valve line 217, which now simultaneously feeds through line 233 the second speed shift cylinders 52a, 175b of the main and pilot gears. The neutral interlock valve 193 thus prevents application of shift pressure until the gear has been neutralized. Completion of synchronism in the pilot gear, which occurs slightly ahead of that in the main gear, due to drive by the upshift gear pair 142, 126, releases the balk splines to permit the sleeve 151 and rod 168 to move right, opening the trip valve 184 to supply trip pressure 208 through the line 209 to shift left the neutral relay valve 191 (opposing line 221 now exhausted). The valve 191 now exhausts the neutralizing cylinder 57 and clutch-release cylinder 44, the latter delayed by a one-way restrictor 205, permitting the shift cylinder 52a to assert itself and establish second speed, which movement operates the neutral valve 58, exhausting the trip line 208, and with it the countershaft brake line 227. Shift is now complete. Downshift sequence differs in the following respects. Downshift leftward movement of the manual selector valve 64 frictionally shifts the director valve 63 leftwards against the stop 89 (position shown in Fig. 1) where it remains for all subsequent downshift and neutral movements. This ensures that, during shift, neutralizing pressure 57 passes through the director valve 63 into the line 229 for introducing the downshift pilot drive gears 141, 136 to cause the pilot gear to synchronize a little ahead of the main gear. The countershaft brake 35 is not applied, but when the main gear is neutralized during shift, the neutral valve 58 supplies pressure through the director valve 63 to shift the clutch relay valve 192, which exhausts the clutch release line 207 so that the clutch reengages and remains re-engaged during subsequent synchronous